1. Field of the Invention
The present invention is directed to a radiation source for generating multi-chromatic, particularly di-chromatic x-radiation, having at least one cathode and an anode for generating x-ray bremsstrahlung and a target surrounded by the anode for converting the x-ray bremsstrahlung incident onto the target into fluorescence radiation.
2. Description of the Prior Art
X-ray sources that generate a continuous x-ray spectrum are almost exclusively employed in medical diagnostics. For a number of applications, however, a monochromatic x-ray spectrum would be advantageous since additional material properties such as, for example, the discontinuous rise in the intensity attenuation at the absorption edges, could thereby be exploited.
Although German OS 42 09 226 discloses a monochromatic x-ray source of the type initially described, this known x-ray source only generates x-radiation at a wavelength defined by the selection of the fluorescence target. Different wavelengths are required, however, for producing images using subtraction techniques. This subtraction method was therefore previously utilized in x-ray diagnostics by employing either x-radiators with continuous bremsstrahlung spectrum and two different acceleration voltages, or a di-chromatic synchrotron source. In the first method with two continuous bremsstrahl spectra shifted relative to one another, however, the absorption edge of the contrast agent is inadequately used. The second approach can be utilized only in conjunction with accelerator rings, and thus not at all in normal hospital use, and moreover requires the use of two-line detectors.